Padlocks have previously been provided in which ends of the shackle are both engaged when the device is locked.
Among such previous padlocks are those in which a single plate is rotated into and out of engagement with the toe and heel of the shackle. Another type captures two balls between recesses in the toe and heel of the shackle and an extension of a longitudinally slideable key plug. Another type of padlock using two balls confines the balls between recesses in the shackle and a rotatable cam to lock the shackle, but this type does not have a removable key-operated cylinder.
The means by which the various members and parts are retained within a padlock body limit the ready exchange of cylinders within a padlock body and previous inventions have not produced a lock which has been acceptable to the locksmiths.